1. Field of the Invention
This invention relates to a method of determining the location of a plurality of laser spots, comprising: determining a first distance of a first laser spot; determining a second distance of the first laser spot; determining a first distance of a second laser spot; determining a second distance of the second laser spot; and adjusting, if necessary, the locations of the first and second laser spots.
2. Description of the Related Art
Prior to the present invention, as set forth in general terms above and more specifically below, it is known, that an optical disc, such as a compact disc (CD), is an electronic data storage medium that can be written to and read using a low-powered laser beam. Optical disc technology first appeared in the marketplace with the CD, which is typically used for electronically recording, storing, and playing back audio, video, text, and other information in digital form. A digital versatile disc (DVD) is another more recent type of optical disc that is generally used for storing and playing back movies because of its ability to store much more data in the same space as a CD.
CDs were initially a read-only storage medium that stored digital data as a pattern of bumps and flat areas impressed into a piece of clear polycarbonate plastic through a complex manufacturing process. However, average consumers can now burn their own CDs with CD players capable of burning digital data into CD-Rs (CD-recordable discs) and CD-RWs (CD-rewritable discs). CD-Rs have a layer of translucent photosensitive dye that turns opaque in areas that are heated by a laser. Areas of opaque and translucent dye vary the disc reflectivity which enables data storage in a permanent manner analogous to the bumps and flat areas in conventional CDs. CD-RWs represent the bumps and flat areas of conventional CDs through phase shifts in a special chemical compound. In a crystalline phase the compound is translucent, while in an amorphous phase it is opaque. By shifting the phase of the compound with a laser beam, data can be recorded onto and erased from a CD-RW.
Methods for labeling the non-data side of such optical discs with text and images, for example, have continued to develop as consumers desire more convenient ways to identify the data they've burned onto their own CDs. Basic methods for labeling a disc include physically writing on the non-data side with a permanent marker (e.g., a sharpie marker) or printing out a paper sticker label and sticking it onto the non-data side of the disc. Other physical marking methods developed for implementation in conventional CD players include ink jet, thermal wax transfer, and thermal dye transfer methods. Still other methods use the laser in a conventional CD player to mark a specially prepared CD surface. Such methods apply equally to labeling CDs and DVDs.
A problem with labeling CDs is that there are no tracks or other markings on the label surface (i.e., the non-data side, or top side) of the CD to determine radial and circumferential positioning. Therefore, the radial and circumferential positioning of a laser spot, for example, to begin printing a label or to append a previously marked label can result in misapplied labels. For example, a label may overlap onto itself if the label data is printed at a radius that is too close to the inner diameter of the disc. Likewise, a label may have gaps if the label data is printed at a radius that is too far from the inner diameter of the disc.
Accordingly, the need exists for a way to determine radial and circumferential positioning on an optical disc surface that has no tracks or other markings, such as the non-data or label surface of an optical disc.
Another problem with labeling CDs is that if multiple laser beams are used to place marks on the label surface, it is difficult to determine the distance between the multiple beams so as to determine the tracks spacing for the disk and drive combination. Therefore, there exists a further need for a way to determine the distance between multiple beams so that the marks can be properly placed on the label surface.
It is apparent from the above that there exists a need in the art for a way to determine the distance between multiple beams so that the marks can be properly placed on the label surface It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.